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Testudo
, , , , , , , , | abbreviation = Tes | genitive = Testudi | pronounce = Tes•tū•dō | symbolism = The | dino = Kojkite | dinoabbrev = Koj | dinogen = Kojkita | dinopronounce = Koj•kīt | mRA = | mdec= | ndec = | sdec = | wRA = | eRA = | quadrant = NQ1 | bordering = Araneus Avis Chtapodi Tarandus | area = 4316.604 sq. deg. (5th) | proportion = 104.637‰ | average = 479.623 sq. deg. (7th) | namedstars = 39 | mainstars = 12 | nakedeyestars = 390 | bfstars = 403 | ehstars = 34 | brightstars = 20 | brighteststar = (1.82 ) | nearbystars = 17 | neareststar = (3.16 , 10.30 ) | messierobjects = 10 | fullrange = 90°N–12°S | partialrange = 12°S–87°S | date = September 12 | solarzodiac = N/A | tropicalzodiac = N/A | siderealzodiac = N/A }} Testudo (Latin for ) is a caelregio with midpoint located in first quadrant of the northern hemisphere. The and cross this caelregio. The northernmost border is just 80' away from the , making it near- . Testudo is composed of nine s (the list is at the top of the infobox to the right). Testudo covers about 105‰ of the sky with an area of 4317 square degrees. is directly named after the where it is now part of in neighboring Chtapodi. Notable stars Bright stars At a of 1.82, an is the Testudo's brightest star, located in . Perseus contains a (2.12m) in addition to Mirfak. The other examples of bright stars in Testudo are * –– a 2.06m located in ; * –– a 2.07m B-type located in Andromeda; * –– a 2.25m located in ; * –– a 2.39m B-type subgiant located in Cassiopeia; * –– a 2.40m K-type supergiant located in ; * –– a 2.44m subgiant located in ; * –– a 2.42m M-type giant located in Pegasus; * –– a 2.49m B-type giant located in Pegasus; and * –– a 2.83m B-type subgiant located in Pegasus. Alpheratz, Scheat, Markab, and Algenib make up the " ," which is a prominent . Nearby stars At a of 10.30 s, the is the Testudo's nearest star, located in Andromeda. Variable stars The can be found in Cepheus. Cepheids are used as s to measure distance of stars in star clusters. The variability period of Cepheids depends on luminosities. When variability period is determined, then its luminosities can be assumed. Using luminosities and magnitudes seen by observer, then distances can be determined. Using this can even measure accurate distances where the distances are too great for current astrometric research to calculate, such as in other galaxies. Another variable in Cepheus is , also known as the Herschel's Garnet Star because of the red color of the star. This star is a and is one of the largest stars known. The star varies between magnitudes 3.62 to 5 over a period of 2 to 2.5 years. Yet another variable in Cepheus is , also properly named Alfirk. The magnitude of this star varies between 3.15 and 3.21 with a period of 4.57163 hours. This star is also a comprising a with a 8th magnitude optical companion. Algol, which is a , is one of the best known and the second (non- ) variable star discovered after . Every 2 days, 20 hours and 49 minutes, the magnitude drops from 2.1 to 3.4 as the fainter star partially eclipses the brighter star, which lasts about 10 hours. To make it more precise, Algol is actually a . is another variable star that is also called "shell star." It is an eruptive variable star that varies irregularly in brightness from 2.20m to 3.40m. This star varies in average brightness by 40% every 50 years. Another eclipsing binary is , located in the open cluster in . SS Lacertae orbits around a every 14.4 days. This eclipsing binary is unique because it turns on and off caused by inclination changes by the gravity of a tertiary star. (19 Piscium) is another variable star, located in Pisces. This star varies brightness irregularly from magnitudes 5 to 6 in about 18 months. Binary stars Alpheratz is a composing of B-type subgiant and A-type main sequence stars. The orbital period around the is 96.7 days at an about 24 s, which is only resolvable in large amateur s. It also contains an optical companion ADS 94 B, which is a 10.8m main sequence star. This companion is 89.3 s away from component A, which can be resolvable using the low-power s but the star is too faint to be seen using binoculars. Planetary systems As of April 2011, there are 34 known s in Testudo. In Cepheus, had the first claimed (named (P9)) found in 1989 but it wasn't confirmed until 2002. In 1995, astronomers found the first ever confirmed exoplanet around a , named (P14) around in Pegasus and is the first ever known. In Andromeda, has four giant exoplanets with orbital periods ranging from 4.6 days to about 38 years; the mass ranges from 1.27 to 6.67 . Upsilon Andromedae became the first normal star discovered to have a multi-planet system. Both (in Pegasus) and (in ) contain s (respectively (P30) and (P161)) that were most studied of all exoplanets, especially their atmospheres. Another star with a transiting planet is (located in Cassiopeia), which has a very eccentric planet (P212). This star also has an unconfirmed second planet (P256). Notable deep sky objects Testudo contains the nearest : the ( 31), located in Andromeda. Andromeda contains two most famous examples of satellite galaxies: and . The (M33) is the second closest spiral galaxy located in . Perseus contains two s (both s) which are the only ones in the sky. One double cluster contains and . Located in Perseus, there is the (also known as Perseus A). Located in Cassiopeia, there is the Tycho's after the progenitor star exploded in 1572. This supernova was seen by . This constellation also contains the ( 1499), which is an . Cepheus contains the ( 1396), which is a concentration of interstellar gas and dust where . Pegasus contains the , which is one of the most compact known. Four of the five galaxies in Stephan's Quintet form a physical association that will most likely end with all four galaxies merging together to form a giant . Vulpecula contains the (also known as the Brocchi's Cluster), which is an clearly seen in binoculars. in Pegasus is one of the densest s in the . This globular cluster contains a million old stars within a diameter of just 120 light-years. In Cassiopeia, the (NGC 7635), which is an and emission nebula, can be found using an . Also in the same constellation, the (IC 1848) which contains the W5 star formation region shaped like a Valentine's heart, can be found using a . The (NGC 604), which is an with massive H II region, can be found in Triangulum Boreale located in the Triangulum Galaxy. This nebula is 1500 light-years or 460 parsecs across, 40 times the size of the Milky Way's . This nebula is over 6300 times more luminous than the Orion Nebula. If Garren Nebula is located at a same distance as the Orion Nebula from Earth, it would appear twice the size of the full moon and outshine . In Cepheus, the (NGC 7023) can be found. This nebula is actually a within the nebula LBN 487. The nebula is lit by a seventh magnitude star , making this a . This nebula is located 1300 light-years away and it is 6 light-years across. In Lacerta, there is the , which was thought to be an irregular variable star in the . This galaxy varies in magnitude just like a variable star, it varies between magnitudes 14 to 17 over a fairly small time periods. Gallery Notable meteor showers The (also called Testudids) peak from between August 9–14 every year. This is caused by the . Up to 142 meteors per hour were visible on August 12, 2010. The most active Perseids in recorded history took place on August 12, 1972 when 292 meteors per hour were visible, roughly twice as active as the 2010 peak. Visibility In the northern hemisphere, Testudo is most prominent from mid summer till late fall. At mid-northern latitudes, about half of Testudo is circumpolar, therefore at least half of this caelregio can still be visible all-year round. However in the mid-southern latitudes, only half of this caelregio can be visible at once, from mid winter till late spring. Zodiac Since the Sun never appears to cross Testudo, this is not a zodiacal caelregio. Category:Articles Category:Caelregios